The invention relates generally to the field of planar lightwave circuits and in particular to a method of defining a waveguide end in a planar lightwave circuit.
Optical fiber is commonly used in telecommunication equipment to carry an optical signal. Optical sub-components, devices and modules, hereinafter generally referred to as optical components typically comprise at least one element which operates on the optical signal. Such an operation may comprise conversion between an electrical signal and an optical signal. Advantageously, optical components are produced in the form of a planar lightwave circuit (PLC), thus allowing for consistent mass production and effective cost reduction.
A major difficulty in the production of optical components is in the stage of aligning an optical fiber with a waveguide of the PLC. Improper alignment leads to significant losses and depreciated performance of the PLC. One well developed technique for aligning an optical fiber with a waveguide involves the use of a v-groove etched into the substrate of the PLC. The fiber is secured in the v-groove, thus ensuring proper alignment in relation to the waveguide. In order to fully expose the end of the waveguide a dice line, or saw cut, is typically made thus also cleaning out the end of the v-groove facing the waveguide. Unfortunately, the facet of the waveguide exposed by a saw cut is not sufficiently clean, and thus polishing of the facet is typically required.
FIG. 1 shows a side view of a PLC based component 10 comprising a substrate 60 and a fiber 30 having core 50. Substrate 60 exhibits v-groove 20, waveguide 40 and trench 70 according to the prior art. V-groove 20 is etched into a portion of substrate 60 so as to accommodate fiber 30. V-groove 20 is dimensioned so as to align core 50 of fiber 30 with waveguide 40. Trench 70 is cut defining a facet of waveguide 40 and cleaning out the end of v-groove 20. Fiber 30 is butt coupled to the facet of waveguide 40.
In order to enable optimum operation of the optical component, the facet of waveguide 40 must be polished prior to bringing the waveguide to a butt coupling with optical fiber 30. This polishing is an additional costly stage in the production of a PLC.
One prior art technique to avoid the extra polishing involves a combination dicing and polishing technique. In this technique, both polishing and dicing are accomplished simultaneously. Unfortunately this technique is somewhat difficult to accomplish in many situations.
Thus, there is a need for an improved method for coupling an optical fiber with a waveguide, and in particular a method that allows for clearing out the end of the v-groove exposing the waveguide end while ensuring a polished facet for the waveguide. Preferably, such a technique will allow for improved coupling of the waveguide with other optical elements used in a PLC.